noun
an inch ahead; the immediate future
Literally 'one sun ahead', used idiomatically to refer to what is just ahead or the very near future, often in expressions like 一寸先は闇 (you can't see an inch ahead; the future is uncertain).
一寸先は闇だから、明日のことは誰にもわからない。
No one knows what tomorrow will bring, because the future is pitch dark.
霧が濃くて、一
The fog is so thick I can't see an inch ahead.